The carbon nanostructure of the present invention is a nanosize material composed of carbon atoms, and for example, carbon nanotube (subsequently referred to as “CNT”), carbon nanocoil (subsequently referred to “CNC”) in which a CNT is formed in the shape of a coil, beaded CNT in which beads are formed on a CNT, cup stack type nanotube formed by bottomless cup-like graphenes stacking on one another, and others are known. Furthermore, a carbon nanostructure that is formed by nanosized carbon materials close-packed in shape of a brush, such as brush-like CNTs, in which CNCs or CNTs are packed closely in shape of a brush, or carbon nanohorns, in which a large number of CNTs whose tip is rolled in shape of a horn are close-packed radially, is referred to as a brush-like carbon nanostructure.
CNT is a pipe-like carbon material whose approximate diameter is about 0.5-10 nm, and whose length of about 1 μm. It is a novel carbon material discovered in 1991 by Iijima. Because CNTs have an extremely minute structure, it is difficult to observe or manipulate them by naked eye, and to improve their handling characteristics and processing property, production of CNT aggregates has been attempted. For example, it is possible to produce a CNT aggregate that can be viewed by naked eye, and as described subsequently in detail, there exists a rope-like CNT aggregate produced by using a so-called CNT structure formed in shape of a brush (subsequently referred to as “rope-like CNTs”).
FIG. 15 is a schematic figure in which the production method of conventional rope-like CNTs 152 is explained. It is possible to produce rope-like CNTs 152, by forming brush-like CNTs 148, oriented substantially perpendicularly with respect to substrate 132, on the surface of said substrate 132, as shown in (15A), and pulling bundle-like CNT aggregate 150, which are adjacently placed, intertwined multiple CNTs 146, by means of tweezers 160, as shown in (15B). That is to say, the manufacturing process of an aggregate comprising of multiple CNTs 146, or so-called rope-like CNTs 152, consists of: (1) the chemical vapor deposition (CVD) process, in which multiple CNTs 146 that are oriented substantially perpendicularly with respect to substrate 132 are formed on a substrate; (2) the cleavage process, in which substrate 132 is cleaved; and (3) the pulling process, in which rope-like CNTs 152 are formed by pulling, multiple CNTs 146 or a bundle-like CNT aggregate 150. In the WO2005/102924A1 pamphlet (patent document 1), production methods of rope-like CNTs, which are a bundle-like aggregate of mutually intertwined multiple CNTs, and of a “CNT sheet”, which is a CNT aggregate of these rope-like CNTs (in patent document 1, it is referred to as a “CNT rope”) that have been assembled in a plane, are described.
In non-patent document 1, a technical explanation is made concerning the temperature increase process of an iron catalyst; where the iron catalyst under a helium gas atmosphere, during a process where the CNT structure growth temperature (700° C.) is reached from room temperature, undergoes a phase transition from the iron elemental state through the magnetite (Fe3O4) state, completing at the iron oxide state of hematite (Fe2O3) at 700° C. (16A) of FIG. 16 is an atomic force microscope (AFM) image of the iron catalyst particle formed by the conventional silicon substrate face mentioned in non-patent document 1. (16B) is an expansion image of the area (length and width both 500 nm) in (16A) indicated by the dotted line. Enlarged catalyst particles, which are aggregates of iron particles that have grown to the catalyst particle diameter of around 100 nm, are formed, and they exceed the particle diameter suitable for the growth of CNTs. Furthermore, the density of the iron catalyst particles is greatly reduced by the formation of the enlarged catalyst particles.    [patent document 1] PCT Publication WO2005/102924A1    [non-patent document 1] Kenji Nishimura, Nobuharu Okazaki, Lujin Pan, and Yoshikazu Nakayama, Japanese Journal of Applied Physics, Vol. 43, No. 4A, 2004, pp. L471-L474